Direktor: Prof. Dr. G. G. Wendt
Direktor: Prof. Dr. Dr. H. Ritter
Mit Unterstützung durch die Deutsche Forschungsgemeinschaft. 相似文献
下载免费PDF全文 Corn leaves did not produce CO2 in the light at any O2 concentration, as was shown by the zero CO2 compensation point and the absence of a CO2 burst in the first minute of darkness. The rate of photosynthesis was inhibited by O2 and the inhibition was not completely reversible. On the other hand, the steady rate of respiration after a few minutes in the dark was not affected by O2.
These results were interpreted as indicating the absence of any measurable respiration during photosynthesis. Twelve different varieties of corn studied all responded to O2 in the same way.
The other 5 monocotyledons studied did produce CO2 in the light. Moreover, the CO2 compensation point increased linearly with O2 indicating a stimulation of photorespiration.
The implications of the lack of photorespiration in studies of primary productivity are discussed.
相似文献 下载免费PDF全文 The rate of protein synthesis is five times lower in cotyledons maintained in 3% O2 than in those maintained in 20% O2. Also net RNA synthesis is almost blocked in 3% O2, while in 20% O2 it proceeds almost linearly for 48 hours.
The different RNA contents cannot explain the different rates of protein synthesis.
The results of shift experiments (cotyledons shifted from 20% to 3% O2 or vice versa) show that the rate of protein synthesis is strictly correlated with actual O2 availability and is largely independent of the one in the previous period. O2 controls the development of the adenylate pool and particularly the increase of ATP level. Thus, both the adenylate pool and the values of the energy charge ratio are lower in cotyledons grown in 3% than in 20% O2.
The shifts of O2 availability induce rapid changes of ATP, ADP, and AMP levels and thus of the values of the energy charge, which are about 0.7 at 3% O2 and higher than 0.8 at 20% O2, independent of previous O2 availability.
The rate of protein synthesis appears to be largely independent of the levels of the single nucleotides and better correlated to the energy charge values.
相似文献 下载免费PDF全文 The rate of apparent photosynthesis was inhibited by O2 while the steady rate of respiration after a few minutes in the dark was not affected. Part of the inhibition of apparent photosynthesis was shown to be a result of increased photorespiration. This stimulation of photorespiration by O2 was manifested by an increase in the CO2 compensation point.
The differential effects of O2 on dark respiration (no effect) and photorespiration (stimulation) indicated that these were 2 different processes.
Moreover the extrapolation of the CO2 compensation point to zero at zero O2 indicated that dark respiration was suppressed in the light at least at zero O2 concentration.
相似文献An experiment was performed to test how different fungal endophyte strains influenced tall fescue’s ability to access P from four P sources varying in solubility.
MethodsNovel endophyte infected (AR542E+ or AR584E+), common toxic endophyte infected (CTE+), or endophyte-free (E-) tall fescues were grown for 90 days in acidic soils amended with 30 mg kg?1 P of potassium dihydrogen phosphate (KH2PO4), iron phosphate (FePO4), aluminum phosphate (AlPO4), or tricalcium phosphate ((Ca3(PO4)2), respectively.
ResultsPhosphorus form strongly influenced plant biomass, P acquisition, agronomic P use efficiency, microbial communities, P fractions. P uptake and vegetative biomass were similar for plants grown with AlPO4, Ca3(PO4)2, and KH2PO4 but greater than in control and FePO4 soils. Infection with AR542E+ resulted in significantly less shoot biomass than CTE+ and E- varieties; there was no influence of endophyte on root biomass. The biomarker for arbuscular mycorrhizal fungi (AM fungi, 16:1ω5c) was selected as an effective predictor of variations in P uptake and tall fescue biomass. Potential acid phosphatase activity was strongly influenced by endophyte x P form interaction.
ConclusionsEndophyte infection in tall fescue significantly affected the NaOH-extractable inorganic P fraction, but had little detectable influence on soil microbial community structure, root biomass, or P uptake.
相似文献 下载免费PDF全文 Both ra and ri increased with depth into the crop. However, ra generally was less than 10% of ri.
Profiles of latent-heat flux density and source intensity of transpiration showed that transpiration corresponded roughly to foliage distribution (with an upward shift) and were not similar to the profile of radiation absorption.
The data were compared with heat budget data. The 2 approaches yielded quite similar height distributions of transpiration per unit leaf area and total transpiration resistance.
The total crop resistance to transpiration was computed as 0.027 min cm−1. This compares to Monteith's values of 0.017 to 0.040 min cm−1 for beans (Phaseolus vulgaris L.), and Linacre's values of 0.015 to 0.020 min cm−1 for turf.
相似文献Plants differ in their ability to use different nitrogen (N) chemical forms, these differences can be related to their ecology and drive community structure. The capacity to uptake intact organic N has been observed in plants of several ecosystems. However, soil organic N uptake by Mediterranean plants is unknown despite organic N being abundant in Mediterranean ecosystems. We compare the uptake of different N forms in two widespread coexisting Mediterranean forest trees with contrasting ecophysiological characteristics: Quercus ilex and Pinus halepensis.
MethodsTo estimate root uptake rate of each N form we used equimolar solutions (1 mM N) of 15NO3 ?, 15NH4 + and 15N-13C glycine.
ResultsNH4 + and glycine were taken up at a similar rate, but faster than NO3 ? in both species. Intact dual labeled glycine was found in both species, demonstrating that both species can absorb intact organic N.
ConclusionsDespite their ecological differences, both species had similar preference for N forms suggesting no fundamental niche complementarity for N uptake. The higher preference for NH4 + and glycine over NO3 ? possibly reflects adaptation to the differing proportions of N forms in Mediterranean soils.
相似文献The litter layer is a major source of CO2, and it also influences soil-atmosphere exchange of N2O and CH4. So far, it is not clear how much of soil greenhouse gas (GHG) emission derives from the litter layer itself or is litter-induced. The present study investigates how the litter layer controls soil GHG fluxes and microbial decomposer communities in a temperate beech forest.
MethodsWe removed the litter layer in an Austrian beech forest and studied responses of soil CO2, CH4 and N2O fluxes and the microbial community via phospholipid fatty acids (PLFA). Soil GHG fluxes were determined with static chambers on 22 occasions from July 2012 to February 2013, and soil samples collected at 8 sampling events.
ResultsLitter removal reduced CO2 emissions by 30 % and increased temperature sensitivity (Q10) of CO2 fluxes. Diffusion of CH4 into soil was facilitated by litter removal and CH4 uptake increased by 16 %. This effect was strongest in autumn and winter when soil moisture was high. Soils without litter turned from net N2O sources to slight N2O sinks because N2O emissions peaked after rain events in summer and autumn, which was not the case in litter-removal plots. Microbial composition was only transiently affected by litter removal but strongly influenced by seasonality.
ConclusionsLitter layers must be considered in calculating forest GHG budgets, and their influence on temperature sensitivity of soil GHG fluxes taken into account for future climate scenarios.
相似文献This study aimed to investigate the effects of coexistence with faba bean, a phosphorus (P)-efficient crop, on soil-accumulated P use by a maize/faba bean intercropping system on dynamic changes in soil P pool.
MethodsMaize and faba bean were grown in P-accumulated soil as either sole cropping or intercropping. After one year (Stage I) or four years (Stage II) of no P application, soil samples were collected respectively and analyzed for soil P pools using sequential fractionation. Aboveground biomass and P content were annually measured from 2013 to 2016 to assess the annual P balance.
ResultsThe intercropped maize/faba bean system showed a P-uptake advantage, with a Land Equivalent Ratio (LER) ranging from 1.2 to 1.5. The average shoot P content over the four years in intercropped maize and faba bean was significantly greater than that of the corresponding sole crops by 29% and 30%, respectively. Over the three-year P depletion period, the three cropping systems primarily depleted the 1 M HCl-Pi fraction, followed by sole maize, which depleted the NaOH-Pi and concentrated HCl-Po fractions. Sole faba bean depleted the alkali-soluble Po fraction (extracted by NaHCO3 and NaOH), and the intercropped maize/faba bean system depleted the conc. HCl-Po fraction, which was similar to the effect of sole maize.
ConclusionsBoth sole crops and intercrops mainly depleted 1 M HCl-Pi, but differed in Po depletion. Sole maize and maize/faba bean intercropping depleted the sparingly labile Po fraction, while sole faba bean depleted the labile and moderately labile Po fractions.
相似文献 下载免费PDF全文 Na-dithionite (Na2S2O4), Na-sulfite (Na2SO3), or ethanol cannot serve as photosynthetic electron donors. However, when these compounds were added to the sulfide-containing system, the need for induction was eliminated. At pH 6.9, in the presence of 3.5 millimolar sulfide, these substances (at concentrations of 10 millimolar, 5 millimolar, or 0.4 molar, respectively) completely abolished the delay preceding sulfide-dependent H2 evolution. It is suggested that all three compounds expose a site capable of directly accepting sulfide electrons.
Only dithionite could adapt the cells to sulfide utilization on its own. Sulfite or ethanol acted only in the presence of sulfide. It is implied that this specific activity of dithionite is related to its characteristic low redox potential.
Sulfide-dependent H2 evolution was insensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, but was inhibited by the plastoquinone antagonist 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, in the presence as well as in the absence of dithionite. In both cases, therefore, the plastoquinone was implied in the electron transport from sulfide.
相似文献Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.
Zur Zeit Gast am Anatomischen Institut der Universität Tübingen. Ständige Adresse: Institut für Histologie und Embryologie der Tierärztlichen Hochschule Wien. 相似文献
下载免费PDF全文 Rate of accumulation of leaf dry matter and rate of export both increased as CO2 assimilation rate increased in each cultivar.
Starch concentrations were greater in Amsoy 71 than in Wells at all CO2 assimilation rates. At low CO2 assimilation rates, export rates in Amsoy 71 were maintained in excess of 1.0 milligram CH2O per square decimeter leaf area per hour at the expense of leaf reserves. In Wells, however, export rate continued to decline with decreasing CO2 assimilation rate. The low leaf starch concentration in Wells at low CO2 assimilation rates may have limited export by limiting carbon from starch remobilization.
Both cultivars exhibited positive correlations between CO2 assimilation rate and sucrose concentration, and between sucrose concentration and export rate. Carbon fixation and carbon partitioning both influenced export rate via effects on sucrose concentration.
相似文献Invertase activity per epicotyl increases relatively more rapidly than does length, reaches a maximum during most active elongation, and declines upon cessation of growth.
GA3 enhances both growth and increase in invertase activity, without altering the kinetics of the 2 processes. If GA3 is added during incubation invertase activity increases more rapidly than does elongation rate.
Incubation of the seedlings in solutions of polyethyleneglycol inhibits the increase of both growth and invertase activity, the latter actually undergoing a decline, but causes no great change in the relative effect of GA3. In presence of polyethyleneglycol GA3 has however a relatively greater effect on invertase activity than on growth.
Sugars in the incubation medium have no significant effect on growth and invertase activity in the epicotyl, except inhibition at relatively high concentrations.
Cycloheximide, actinomycin D, and 5-fluorodeoxyuridine (FUDR) inhibit both growth and the increase in invertase activity. Added during incubation cycloheximide causes complete inhibition of growth and a decrease in invertase activity with no appreciable lag phase. With actinomycin D and FUDR the inhibition occurs after lag periods of 2 to 3 and of at least 10 hours, respectively. Thus the increase in enzyme activity is very probably based on de-novo synthesis, and the enzyme is in a state of turnover during growth.
The enzyme is present in soluble form in the cytoplasm, not firmly bound to any cell structures.
相似文献Understanding the influences of environmental variation and anthropogenic disturbance on soil respiration (RS) is critical for accurate prediction of ecosystem C uptake and release. However, surprisingly, little is known about how soil respiration and its components respond to grazing in the context of global climate change (i.e., precipitation or nitrogen deposition increase).
MethodsWe conducted a field manipulative grazing experiment with water and nitrogen addition treatments in a meadow grassland on the Songnen Plain, China, and assessed the combined influences of grazing and global change factors on RS, autotrophic respiration (RA), and heterotrophic respiration (RH).
ResultsCompared with the control plots, RS, RA and RH all exhibited positive responses to water or nitrogen addition in the wet year, while a similar effect occurred only for RH in the dry year. The responses of RS to precipitation regimes were dominated by both frequency and amount. However, grazing significantly inhibited both soil respiration and its components in all subplots. Further analysis demonstrated that the plant root/shoot ratio, belowground biomass and microbial biomass played dominant roles in shaping these C exchange processes.
ConclusionThese findings suggest that changes in precipitation regimes, nitrogen deposition, and land utilization may significantly alter soil respiration and its component processes by affecting local carbon users (roots and soil microorganism) and carbon substrate supply in meadow steppe grasslands. The future soil carbon sequestration in the studied meadow steppe will be benefited more by the moderate grazing disturbance.
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